The University of Kentucky College
of Agriculture releases the results of a recently completed experiment conducted
to determine if eastern tent caterpillars (ETC) induce fetal loss in domestic
pigs. This is the fifth in a series of ongoing experiments designed to identify
the factor or agent responsible for fetal losses due to Mare Reproductive Loss
Syndrome (see MRLS reports of June 12, 2002, October 25, 2002 and June 6, 2003,
at this WEB site: www.uky.edu/Agriculture/VetScience/mrls/index.htm).
These experiments are funded by the University of Kentucky College of Agriculture
and USDA:ARS.

Eastern Tent Caterpillars (ETC) were
collected in central Kentucky in the spring of 2003 and stored at -80ºC
until used. Gilts in mid-gestation were paired so that one gilt from each pair
was fed a normal ration (n=5 gilts) and the second gilt of each pair received
ETC (40 g/gilt/day for 10 days) mixed into the normal ration. Two of five gilts
fed ETC aborted their entire litters while none of the five control gilts aborted.
The two ETC-fed gilts which aborted, along with their non-treated pairs, were
euthanatized and necropsied 1-3 days after the abortions occurred. The remaining
gilts were euthanatized and necropsied 29 days after the onset of the trial.
Streptococci bacteria were isolated from fetuses of all gilts fed ETC, whether
or not they aborted, and from fetuses of one control gilt. Bacteria isolated
from the control fetuses were less numerous and of a different strain than those
isolated from fetuses of ETC-treated gilts. Of particular interest was the identification
of what appear to be caterpillar setae (hairs) in the alimentary tract of gilts
fed ETC but not of control gilts. At this time we cannot be certain if the hairs
contributed to the abortions in the two treated gilts or to the presence of
bacteria in fetuses of the treated gilts.

This experiment demonstrated for
the first time that ETC can cause abortion in a non-equid in a manner consistent
with MRLS, and indicates that domestic pigs may be a useful model for studying
the syndrome.